Reverse fold self-opening plastic square bottom bag

ABSTRACT

A flat-bottom plastic bag produced from an extruded length of gusseted and thermoplastic material including the steps of sealing and severing a length of such material to provide a closed bottom; folding the upper portion of each gusset inwardly toward the center of the bag to create triangular portions at the bottom of each gusset, the bottom corners of the bag tapering inwardly with the taper being determined by the outer leg of each triangular portion; opening the folded gusset portions to a flattened position, each triangular portion being folded simultaneously along a median line and the inwardly tapered bottom configuration of the bag being retained; folding the tapered bottom portion of the bag upwardly toward the front of the bag thereby creating a transverse fold line extending from edge to edge of the bag, the height of this folded portion being substantially identical to the height of the folded median line of each triangular portion, the height of this median line being substantially identical to the depth or width of the gusset; and opening said upwardly folded portion, for packing and/or shipping purposes, to a plane contiguous to that of the remainder of the bag. The invention also contemplates the novel bag produced by the above method.

United States Patent [191 Platz et al.

[4 1 Nov. 4, 1975 REVERSE FOLD SELF-OPENING PLASTIC SQUARE BO'ITOM BAG[75] Inventors: Gerald M. Platz, Champaign; James B. Honn, Arcola, bothof I11.

[73] Assignee: National Distillers and Chemical Corporation, New York,NY.

[22] Filed: Nov. 7, 1973 [21] Appl. No.: 413,467

Related US. Application Data [62] Division of Ser. No. 243,946, April14, 1972, Pat.

[52] US. Cl 229/58; 229/61 [51] Int. Cl. B65D 33/00 [58] lh'eld ofSearch 229/57, 58, 61

[56] References Cited UNITED STATES PATENTS 227,147 5/1880 Campbell229/61 3,739,977 6/1973 Shapiro et a1 229/58 X PrimaryExaminer-William 1. Price Assistant ExaminerStephen P. Garbe Attorney,Agent, or FirmAllen A. Meyer, Jr.

[57 ABSTRACT A flat-bottom plastic bag produced from an extruded lengthof gusseted and thermoplastic material including the steps of sealingand severing a length of such material to provide a closed bottom;folding the upper portion of each gusset inwardly toward the center ofthe bag to create triangular portions at the bottom of each gusset, thebottom corners of the bag tapering inwardly with the taper beingdetermined by the outer leg of each triangular portion; opening thefolded gusset portions to a flattened position, each triangular portionbeing folded simultaneously along a median line and the inwardly taperedbottom configuration of the bag being retained; folding the taperedbottom portion of the bag upwardly toward the front of the bag therebycreating a transverse fold line extending from edge to edge of the bag,the height of this folded portion being substantially identical to theheight of the folded median line of each triangular portion, the heightof this median line being substantially identical to the depth or widthof the gusset; and opening said upwardly folded portion, for packingand/or shipping purposes, to a plane contiguous to that of the remainderof the bag. The invention also contemplates the novel bag produced bythe above method.

3 Claims, 11 Drawing Figures IIS. Patent NOV.4, 1975 Sheet1of3 3,917,159-

' U.S. Patent Nov. 4, 1975 sheet 3 on 3,917,159

REVERSE FOLD SELF-OPENING PLASTIC SQUARE BOTTOM BAG This application isa division of application Ser. No. 243,946 filed Apr. 14, 1972 and nowU.S. Pat. No. 3,799,042.

This invention relates to reverse fold self-opening plastic squarebottom bags.

Essential requirements of bags of the character with which we here areconcerned are that the bags must include a substantially rectangular andflat-bottom surface and the gauge or thickness of the thermoplasticsheet material employed must be such that the bag walls will beself-sustaining; thus, the bag will stand erect, resting securely uponits flat bottom, when in opened position and filled or partially filled.

An important end use of such bags is as a carry-out bag of various sizesfor the replacement of paper bags commonly used in the grocery and supermarket industries. Present practices in these fields require that thepaper bags utilized be of double-wall manufacture, or that two bags ofheavy weight paper (one inside the other) be employed, thereby seekingto eliminate'the hazards of bottom or sidewall breaks occasioned byover-loading, wet groceries or other goods, and other influences thatprovide stresses or conditions beyond the tolerance of the paper stock.Mounting costs in connection with the provision of paper carry-out bagswhich will withstand satisfactorily the adverse conditions referred tohereabove provide continually increasing problems and the presentinvention is directed to the solution thereof.

Bags of the character with which we here are concerned are commerciallyavailable to a degree; however, problems inherent to known methods ofmanufacture (particular reference is had to the folding of the bag sothat it will open readily and stand upon its flat bottom when filled orpartially filled) have added materially to the costs. It is a majorobject of the present invention to provide a novel method of manufactureand folding whereby such bags can be produced with greater economy thanhas been known heretofore.

It is further object of the present invention to provide a plastic bagwhich will be moisture-proof and will have adequate wall strength towithstand interior stresses when the bag is loaded.

It is still further object of the present invention to provide a novelplastic bag having a flat, substantially rectangular bottom surface,whereby the bag may be opened readily and stand erect to permit theconvenient utilization thereof for all commerical purposes where bagsmay be desirable including along a filling and check-out line.

A still further object of the invention is the production of a bag ofthe character with which we here are concerned from a continuous lengthor tube of heatsealable thermoplastic material which has been extrudedand flattened to provide a gusset at each side thereof, externaltransverse sealing and severence or perforation between adjacent bagsbeing accomplished after the formation of such gussets.

It is an additional important object of the invention to provide a bagof the character under discussion which may be produced with particulareconomy, can compete successfully with prior art paper bags, and may beused with particular ease in grocery and super market operations, or thelike.

Further objects and advantages of the invention will be readily apparentfrom the following description, taken in conjunction with theaccompanying drawings, wherein:

FIG. 1 is a fragmentary perspective view of the bottom portion of a flatbottom plastic bag produced in accordance with the present invention;

FIG. 2 is a transverse sectional view, on an enlarged scale, taken onthe line 22 of FIG. 1;

FIG. 3 is a plan view of a length of gusseted, thermoplastic tubularmaterial, sealed along the bottom edge thereof and illustrating theinitial step of the novel method of the present invention;

FIG. 4 is a transverse sectional view, on an enlarged scale, taken onthe line 44 of FIG. 3.

FIG. 5 is a fragmentary sectional view of the lower extremity of thebag, illustrating the second step of the present method, the openportion of each gusset having been folded inwardly toward the center ofthe bag;

FIG. 6 is a detail transverse section view, on an enlarged scale, takenon the line 66 of FIG. 5;

FIG. 7 is a fragmentary plan view, similar to FIG. 5 and illustratingthe third step of the method, the folded gusset portions having beenopened outwardly and returned to the original positions thereof;

FIG. 8 is a transverse detail sectional view on an enlarged scale takenon the line 8-8 of FIG. 7;

FIG. 9 is a plan view of the lower extremity of the bag, similar toFIGS. 5 and 7 illustrating the fourth step of the present method, theclosed bottom of the bag having been folded upewardly to a planeimmediately above that of the remainder of the bag;

FIG. 10 is a detail vertical sectional view on an enlarged scale takenon the line 10-10 of FIG. 9; and

FIG. 11 is a plan view similar to FIG. 9, illustrating the final step ofthe present method, the upwardly folded bottom portion of the bag havingbeen returned to a plane contiguous to that of the bag proper.

As shown in the drawings, particular reference being had to FIG. 3, thetube 10 of the present invention has been heat-sealed transversely alongthe bottom edge and severed, forming a length of seamless thermoplastictubing produced by an extrusion process and flattened as is well-knownin this art. The severed bag includes a front wall 11 and a rear wall 12united along the longitudinal thereof by gussets l3 and 16 as is wellknown in this art. Gusset 13 is constituted by an upper portion 14 and alower portion 15; similarly, the opposed gusset 16 is constituted by anupper portion 17 and a lower portion 18.

The thermoplastic material or tube is heat-sealed transversely from edgeto edge thereof, as indicated at 19, and then severed, thereby providinga bottom closure for the initial bag and an open mouth edge for the nextadjacent bag, the invention contemplating the successive production ofbags from a continuous length of tubing. It will be noted that thetransverse seal 19 securely unites or welds the bottom edges of thefront and rear walls of panels 11 and 12 to each other and that thisseal also includes the gusseted portions 13 and 16. Thus, in the centralportion of the sealed tube there are two layers of thermoplasticmaterial, constituting the front and rear walls of the bag; however, inthe outer portions of the seal 19 there are four layers of thermoplasticmaterial, constituted by the two opposed layers 14 and 15 of the gusset13 and the comparable layers 17 and 18 of the gusset 16 which areheat-sealed between the front and rear walls 11 and 12.

The bottom-sealed bag is then placed upon a suitable support and theupper portion of each edge gusset is folded reversely toward the centerof the bag, to the position illustrated in FIG. 5 of the drawings. Thisfolding operation creates a double-walled triangular por tion along thelower extremity of the gusset l3 and a companion double-walledtriangular portion 21 along the lower extremity of the gusset 16. Thelower wall of each of the triangular portions 20 and 21 is constitutedby the tubular material on both sides of the opposed extremities of thesealed bottom portion; the upper wall of each triangular portion iscontiguous with the lower wall thereof and is constituted by theimmediately adjacent portion of the associated gusset.

The vertical center line of the outer surface or wall of each of thesetriangular portions is constituted by an extremity of the sealed bottomedge 19 and the bottom corners of the bag are inwardly tapered asindicated by the outer folded edge 22 of the gusset triangle 20 and theouter folded edge 23 of the triangle 21. In this reverse foldingoperation of the upper portion or edge of the gussets, a vertical creaseor fold line 24 is created along the front wall of the bag in alignmentwith the center or depth fold of the gusset 13 and a similar verticalcrease or fold line 25 is created along the front bag wall in alignmentwith the center or depth fold of the gusset 16.

The next step of the present process is disclosed in FIG. 4 of thedrawings where the gussets l3 and 16 are opened outwardly and returnedto their original positions. It will be noted however that this sameopening or return folding operation also extends across the twotriangular portions 20 and 21 and, as shown clearly in FIG. 8 of thedrawings, the extremity of the sealed bottom edge 19 within eachtriangular portion assumes a vertical position centrally of therespective gusseted portions 13 and 16.

The halves of the folded triangular portions 20 and 21 are mirror imagesof each other. Thus, the triangular portion 20 has an angular edge 26extending at right angles with respect to the edge 22 and the upperextremities of these triangular portions are contiguous with the foldededge 27 which is parallel to the bottom seal 19 and extends the fullwidth of the gusset l3. Similarly, the triangular portion 22 has anangularly directed folded edge 28 also disposed as a right angular or 90relationship with respect to the folded edge 23 and the upperextremities of the edges 28 and 23 are contiguous with the folded line29 extending across the full width of the gusset 16 and also disposed inparallel relationship with respect to the sealed bottom 19.

The lower extremity of the sealed bag is then folded upwardly andtransversely from edge to edge, as indicated at FIG. 9 of the bag, tocreate a folded line 30 extending across the entire front wall of thebag and a companion fold line 31 extending across the entire rear wallof the bag, the location or plane of these fold lines 30 and 31 being inthe identical plane as the folded edges of the triangular portions 27and 29, respectively, of the triangular portions 20 and 21.

This completes the folding step required to produce the bag of thepresent invention. However, for convenience in packing and shipping, thebottom folded portion of the bag is first straightened to the plane ofthe remainder of the bag as illustrated more particularly in FIG. 11 ofthe drawings.

A simple grasping of one wall of the bag mouth and a swinging, openingoperation, will produce a self-sup- 4 porting flat-bottom plastic bag,when an article or. the like will have been placed therein, the lowerportion of which is illustrated in FIG. 1 of the drawings.

It will be understood that the formation of the trans- I which extend,respectively, across the associatedgussets.

This is illustrated more particularly in FIGS. 1 and 2 of the drawingswhere, it will be observed, the flat bottom of the opened bag is definedby (a) the fold line 30 extending across the bag front wall 11, (b) thefold line 31 extending across the bag rear wall 12, (c) a fold line 32extending across the gusset l3, and (d) the fold line 33 extendingacross the gusset 16. The vertical edges of the opened bag are definedby the edge folds of the opened gussets 13 and 16 and the depth of theopened bag is determined by the width of the Hat bottom portion which isidentical to that of the fully opened or extended gussets.

In practice, highly satisfactory flat-bottom plastic bags have beenproduced from blown tubular film having a thickness or gauge on theorder of 3 mils. Where the tube as blown has a circumference on theorder of 36%. inches, a bag having a width of 11% inches with 3% incheslay-flat gussets is particularly suitable for present purposes. Thesealed and severed tube, prior to the bottom-forming operation, has alength on the order of 2l inches and, when bottom forming will have beencompleted, a flat bottom having a width of 11% inches and a depth of 6%inches (approximately twice the depth of the lay-flat gusset) iscreated. Such a bag can be snapped open, as is cutomary in baggingopera.

tions, with particular ease and, when provided from 3-mil film, willhave self-sustaining walls and willremain erect andopen during thefilling operation.

Where the heat seal can be accomplished in 1% seconds, the film blowing,gusseting and flattening, and bag forming can be completed in line as acontinuous operation. Alternately the gusseted flat tube may be providedin roll form or sealed and severed lengths may be fed to the apparatusfrom a stacked supply thereof While the continuous method of operationwill make for improved economy, under any of these circum-.

resistance to rupture under stresses vastly in excessof those to beexpected under normal conditions, and will be fluid-proof as againstboth internal and external adverse influences. Bags of this charactermay be manufactured with equal facility through a particularly widerange of sizes with appropriate adjustment of the appa-f ratus tocompensate for bag width, length, and gusset depth;

Any thermoplastic film having satisfactory properties of strength,stiffness and heat scalability can be used in accordance with thisinvention, such as polyolefins, polyamides (nylon), polyvinyl chlorides,polyvinylidene chlorides, polyesters, polycarbonates, and polystyrene,and the like. Polypropylene and polyethylene are preferred. Linear highdensity polyethylene having a density in the range of about 0.945 to0.960 is especially preferred.

Typical properties of films found to be satisfactory for the presentinvention are:

Modulus, p.s.i. (1% secant): (ASTM D88267) T.D. 140,000-220,000 Tensile,p.s.i.

T.D. moo-5.000 Elongation, percent:

The thickness of the film is not critical and will vary with the otherproperties depending on the desired stiffness and strength of the bag.Economy will be another factor which determines how thick the film willbe. Typical thicknesses are in the range of about 1.0 to about 50 mils.

While the invention has been exemplified in some detail in connectionwith plastic bags of substantial size and produced from material havinga relatively thick gauge, it will be understood that the presentinventive concept is applicable equally to any gusseted bag of thecharacter with which we here are concerned without regard to the sizethereof or the gauge of the thermoplastic material or film from whichsuch bags are produced.

Further, it is within the purview of the invention that such reversefold plastic bags may be in the form of a continuous roll where aperforation or the like is provided immediately adjacent each bottomheat seal and successive bags can be separated from the prefabricatedendless roll or length, with particular convenience, as required. Such alength of prefabricated bags also could be packaged in either flat orroll form in a dispenser box for convenient home or commercial use.

It will be obvious to those skilled in the art that various changes maybe made in the invention without departing from the spirit and scopethereof. .Thus, the invention is not considered limited by that which isshown in the drawings and described in the specification, and referenceis had to the claims for summaries of the essentials of the invention,novel features of constructions, and novel methods of operation, for allof which protection is desired.

What is claimed is:

l. A flat-bottom bag produced from thermoplastic material includingfront and rear walls united along each longitudinal edge by a gusset,said bag having been heated sealed transversely and severed adjacent oneextremity to provide a bag having a closed bottom and an open mouth,each bottom corner of said bag including an upwardly directeddouble-walled triangular portion folded along a vertical median linethereof, said median line being in a plane substantially identical tothe plane of the inner edge of the associated gusset, the median line ofeach folded double-walled triangular portion being constituted by anincluded extremity of the transverse bottom seal and said bag havinginwardly tapered corner portions defined by the overlying edges of saidfolded double-walled triangular portions, and fold lines extendingacross the front and rear walls to provide the longitudinal edges of theflat bottom of said bag, the spacing of each of said transverse foldlines from the bag sealed bottom edge being substantially identical tothe depths of said gussets.

2. A flat bottom bag comprising a length of seamless tubularthermoplastic film having top and bottom edges and four axial fold linestherein to provide front and rear walls united along each longitudinaledge by a gusset, the bottom edge of said tubular film being heatsealedto provide a bag having a closed bottom and an open mouth, the bottomseal being folded inwardly at the mid-point of each gusset toward thecenter of the bag to create an inwardly directed double wall triangularportion folded along a vertical median line of each bottom corner of thebag, said vertical median line being substantially coplanar with theinner edge of the associated gusset, the vertical median line of eachfolded double wall triangular portion being constituted by the includedextremity of the bottom seal, said bag having inwardly tapered cornerportions defined by the overlying edges of said folded double walltriangular portions, and transverse fold lines extending across thefront and rear walls to provide the longitudinal edges of the flatbottom of the bag, the spacing of each of said transverse fold linesfrom the bag sealed bottom edge being substantially identical to thedepth of said gusset.

3. The flat bottom bag of claim 2 wherein each gusset has an additionalaxial fold line at the mid-point thereof and parallel to said four axialfold lines.

1. A flat-bottom bag produced from thermoplastic material includingfront and rear walls united along each longitudinal edge by a gusset,said bag having been heated sealed transversely and severed adjacent oneextremity to provide a bag having a closed bottom and an open mouth,each bottom corner of said bag including an upwardly directeddouble-walled triangular portion folded along a vertical median linethereof, said median line being in a plane substantially identical tothe plane of the inner edge of the associated gusset, the median line ofeach folded double-walled triangular portion being constituted by anincluded extremity of the transverse bottom seal and said bag havinginwardly tapered corner portions defined by the overlying edges of saidfolded double-walled triangular portions, and fold lines extendingacross the front and rear walls to provide the longitudinal edges of theflat bottom of said bag, the spacing of each of said transverse foldlines from the bag sealed bottom edge being substantially identical tothe depths of said gussets.
 2. A flat bottom bag comprising a length ofseamless tubular thermoplastic film having top and bottom edges and fouraxial fold lines therein to provide front and rear walls united alongeach longitudinal edge by a gusset, the bottom edge of said tubular filmbeing heat-sealed to provide a bag having a closed bottom and an openmouth, the bottom seal being folded inwardly at the mid-point of eachgusset toward the center of the bag to create an inwardly directeddouble wall triangular portion folded along a vertical median line ofeach bottom corner of the bag, said vertical median line beingsubstantially coplanar with the inner edge of the associated gusset, thevertical median line of each folded double wall triangular portion beingconstituted by the included extremity of the bottom seal, said baghaving inwardly tapered corner portions defined by the overlying edgesof said folded double wAll triangular portions, and transverse foldlines extending across the front and rear walls to provide thelongitudinal edges of the flat bottom of the bag, the spacing of each ofsaid transverse fold lines from the bag sealed bottom edge beingsubstantially identical to the depth of said gusset.
 3. The flat bottombag of claim 2 wherein each gusset has an additional axial fold line atthe mid-point thereof and parallel to said four axial fold lines.